Various wireless standards, such as Institute of Electrical and Electronics Engineers (IEEE) standards 802.11a/b/c/d/e/f/g/h/i/j/k/ (referred to collectively as IEEE 802.11), provide for wireless connectivity between wireless devices, such as, for example, between a wireless station and an access point connected to an infrastructure network. These wireless standards typically provide processes for managing the power consumption of the wireless devices in an attempt to minimize the power consumed by the wireless devices, which generally are battery powered and therefore have a limited supply of power.
One technique frequently used to minimize the power consumption of a wireless device includes increasing the transmission rate (also referred to as the PHY rate) of the wireless device. It will be appreciated that increasing the transmission rate reduces the power consumption as the time needed to transmit information is reduced, thereby reducing the duration that the antenna of the wireless device is active while transmitting the signal representative of the information. However, the maximum transmission rate supportable between wireless devices may be limited for any number of reasons, such as, for example, the distance between wireless devices, the presence of noise or other interference, the individual capabilities of the wireless devices, and the like.
In addition to, or instead of, implementing the maximum supportable transmission between wireless devices, a reduction in the transmit power used by a wireless device may be performed to further reduce the power consumption of the wireless device. The degree to which the transmit power of a transmitting wireless station may be reduced generally is related to the link margin of a receiving wireless device, where the link margin typically represents a ratio of the actual received signal power to the minimum received signal power desired or acceptable by the receiving station. Thus, the transmitting station, in theory, could reduce its transmit power by an amount up to the link margin of the receiving wireless device without violating the minimum received signal power requirement of the receiving wireless device. To illustrate, assuming that a receiving wireless station receives a frame at a particular transmission rate with a signal-to-noise ratio (SNR) of 25 decibels (dB) and further assuming that the receiving wireless station is formatted to require a minimum SNR of 12 dB for the particular transmission rate. From these values, the link margin for the receiving wireless station may be calculated as 13 dB (25 dB−12 dB). Therefore, in this example, the transmitting wireless device could reduce its transmit power by up to 13 dB while still transmitting with enough power to satisfy the minimum requirements of the receiving wireless device.
While the reduction of transmit power commensurate with the link margin of a receiving wireless device can significantly reduce power consumption by a transmitting wireless device, conventional wireless devices typically transmit at the maximum power level permitted by the characteristics of the device or as permitted by regulation (e.g., radio power transmission regulations promulgated by the Federal Communications Commission) because they are unaware of the link margin of the receiving wireless device. As a result, excessive power is consumed as the transmitting wireless station transmits information at a transmit power significantly higher than would otherwise be necessary.
Accordingly, techniques for minimizing the transmit power of a transmitting wireless device in view of the link margin of a receiving wireless device would be advantageous.